Written by the One True Author, Randall Munroe, this comic is unique among the xkcd canon because its frame updates hourly. The first frame of Time appeared on 2013-03-25 at midnight Eastern Daylight Time. A new TimeFrame appeared every half-hour after that until 2013-03-30, when the interval between frames was lengthened to one hour. Ever since then, the frame has continued to update at the top of the hour. It Ended on 2013-07-26. There are 3101 individual frames of Time.
The story of Time concerns the adventures of two people, referred to by the users of its xkcd discussion thread as Megan and Cueball. The pair construct a sandcastle on a beach, then set off on a journey to find answers to phenomena they do not understand (Why is the Sea rising?). When they finally discover the answers they have been looking for, they realize that their home is in danger and return to save their people.
Like all xkcd comics, the One True Comic has title text (often incorrectly referred to as alt-text). For over 2900 frames, it read "Wait for it." When the protagonists learn that their home is in danger, the title text changed to read "..." and in the very next frame, it changed again to say, "RUN."
On newpix m3067, when Megan says, "We're going to have to ride it out," the title text changed yet again, from "RUN." back to "..." (an ellipsis). For a brief time during that newpix it actually consisted of four periods instead of the standard three, like this: "...." but was changed to the correct three-dot ellipsis somewhere between the :15 and :25 mark.
Readers of the One True Thread took the first incarnation of the title text as instruction by Great Lord Randall to the xkcd audience - after all, the frame would keep updating. It may also be a reference to past xkcd comic experiences, such as #1110, Click and Drag, where members of the audience managed to "cheat the system" and provide shortcuts so that the general public could jump to exciting revelations without having to explore the entire comic themselves. So far, no one has managed to cheat Time and retrieve future frames. "Wait for it" is a very common theme of the discussion thread.
The second and third incarnations of the title text appear not to be instructional to the xkcd audience. "..." and "RUN." may reflect the internal thought processes of the protagonists Cueball and Megan. Alternatively, "RUN." may be instructional to these characters. Timewaiters have recently begun to humorously interpret "RUN." as instructional to the xkcd audience as well, supposing that the One True Author wants his audience to go out and exercise.
The fourth incarnation of the title text caused some confusion at first, because of the erroneous fourth period. Many OTTers expected it to last for just one newpix, like the first ellipsis. However, it has not yet changed,
Plot (Incomplete) Edit
Two people, Megan and Cueball, sitting on a beach, with nothing to do, get bored. After Cueball tests the temperature of the water, Megan decides to build a sandcastle, and is immediately joined by Cueball. As they go from a single tower to a castle wall, Cueball leaves Megan for some as yet unknown reason. Megan, who seems passionate about the castle, quickly expands the castle wall. Upon finishing an arch and pilling sand, Cueball arrives back to finish the sandcastle, only Megan leaves during this process. Being careless, Cueball accidentally crushes the sandcastle as he climbs down it. Soon after rebuilding, Cueball leaves yet again.
The frame then pans out to reveal a greater image, showing another bigger sandcastle, including towers with flags on top. Megan places flags on the first castle and then sits next to the water. Cueball joins her, then she asks "WANNA SWIM?", to which he replies "YEAH." and they both walk towards the water and disappear. Shortly after, they return with Megan exclaiming "PFFTHH" *Cough*. Cueball replies (still out of frame) "You ok?" Megan then replies "Just got some in my mouth." Megan then walks back up the beach and disappears out of frame. Cueball follows but pauses to look back at their first sandcastle. Then he removes two flags from two towers and starts to connect the castles in between. He slowly creates a bridge to connect the castles. Then, just as he is finishing, Megan sets up a trebuchet to destroy part of what Cueball has done. Both go off panel again just in time to avoid an almost vertically launched shot from the trebuchet.
Megan and Cueball return once again. Cueball simply repairs the end of the castle where the last trebuchet shot hit and leaves. Megan starts building a large mound where the two arches were. At one point she stops to lie down on top of this structure, then gets up and resumes building. Eventually Cueball returns and builds a miniature version of the entire sandcastle system on top of this mound. Megan gets a miniature trebuchet, places it on the miniature sandcastle, and it works! Cueball and Megan then leave the panel again.
Megan returns with some very long poles and places them behind the sandcastle. Then she places them upright with the help of Cueball. These poles dwarf even the sandcastle. They then secure a platform on top of the poles. Cueball then tastes the seawater while Megan goes off-panel.
Megan returns and builds a dike to protect against the incoming sea. She then extends the platform on top of the poles, and Cueball then extends it further. They then build more sandcastles and platforms on top of this platform. While Megan asleep, LaPetite appears, and then leaves again.
Megan and Cueball discuss the nature of the sea and the rivers, and wonder why the sea is rising. Cueball says "We have no idea what's out there" to which Megan replies "Yeah." and after a pause "Wanna find out?"
Megan and Cueball leave, apparently to explore. Megan returns briefly to put a small flag on the leftmost tower and say "bye". The frame then fades away to white.
The story then picks up with Cueball and Megan walking with bags across a relatively level surface. The terrain looks like frame 1, albeit from a wider angle, showing they are walking along the coast. The scene shifts multiple times between views of them to the left of a river, and 90° rotated views of them walking overland, generally upstream. Sometimes these shifts in angle are marked by corresponding shifts between front and profile views of their bodies.
Megan indicates she has never been so far "this way". They reach a river they haven't seen before. Cueball slips in and loses his bottle. He contemplates swimming out to get it, but Megan says it is too dangerous. Later when Megan gets too close to the edge, Cueball senses danger and pulls her back.
After a small talk both agree to find a ford. After walking for a while, Megan realizes that the river was wider than they realized. The branch of the river they were walking along joins up with another branch and the opposite bank eventually comes into view.
They stop for a break and Cueball dozes off and mumbles in his sleep. They discuss this river and the difference between it and theirs. First mention of other people. They decide to continue upriver.
The terrain begins to slope noticeably uphill. They wonder if others have noticed the rise of the ocean and mention that they live in tents. They walk deeper into the dunes, having fun by jumping and sliding. Megan falls after jumping too high.
A bird appears in the sky. They watch it until it's gone, then begin walking again. Some vegetation appears, grass and then small trees. They stop and nap beneath a greater tree, seeming to have never seen one before.
After a rest Cueball goes off to explore. He picks some berries and examines a campfire pit, then walks back to Megan and shares his findings. They wonder why the other people have left.
They stop at the river to drink, then climb a ridge, and are awestruck by two tall trees. As they walk through the trees, the first tree has markings on the trunk and the fourth tree has a strangely bent top, and they comment on these features before they continue on and past three more huge trees and a regular sized tree to enter what looks like a vineyard. They eat some grapes.
The two travel on. Cueball encounters a snake while climbing a small cliff and falls back. They find another section of the cliff and continue. After that they reach a tree with a nest in it with a young baby bird crying for food. The chick's mother feeds whom, then Cueball takes a short nap while Megan investigates a small river.
The pair continue to climb the mountain, commenting here and there on the possibility of turning back, but Megan wants to see what's at the top. Eventually, they stumble upon a small shelter and a few other signs of inhabitants. They investigate the surrounding area.
A cougar attacks Megan, but Cueball gets in the way—although not before one claws her leg. Most of the hit gets absorbed by his backpack, but Cueball is forced to the ground. Megan grabs a stick and attacks the cat, which runs away.
Megan decides she would like to press on despite her injuries. Cueball and Megan then take turns sleeping as night arrives. Cueball takes the first watch. While Megan sleeps a meteor appears in the sky. Then Megan takes the next watch. When Cueball wakes up, they start their journey again up the mountain, which is slower due to Megan's injuries as Cueball has to help her over some of the steeper climbs.
After they reach a plateau there is a tower. Megan climbs up and sees other people. Cueball is curious and climbs the tower too. On top of that tower Megan remarks her wound doesn't hurt much when walking but it does when she climbs.
Then, they continue their travel at the plateau. They run into three people who speak a language that they are unable to understand. Despite the language barrier, Megan shows her wounded leg and the strangers proceed to take a closer look at her. The strangers then help her to sit down on a stone. After the stranger with the medical equipment is back they do some kind of first aid. Megan expresses her thanks, and the strangers indicate that they should follow.
After walking uphill again they approach another tower. A device is mounted to the top and smaller devices are around. They drink some water there and Cueball learns his first word in this new language: "water" or "drink". () To aid communication, they start to draw pictures on the ground. Cueball shows their travel from the sea to the current location, and the stranger adds the rising sea level, indicating that he knows about this happening. The stranger shows a castle some more uphill and a long-haired woman behind it. Cueball hopes they can speak to her, and the stranger explains with a drawing that it's lesser than a day away. The strangers collect their devices and store them somewhere. Then they start the travel to the castle. When they rest, Megan and Cueball taste some food offered by the strangers; they like it. A flag appears and they encounter a small city. A big castle, still under construction, is visible in front of them. Megan states that she never thought she would ever see a real castle. On their way to the castle they meet another stranger, exchanging some greetings. Then they enter the castle.
The five people walk down a stairway and enter a great hall. Great windows showing a dazzling light are high above them. They approach a long-haired woman at a desk who greets them. After Cueball asks, it appears she can "somewhat" understand him and Megan. The woman asks where they came from and asks about their home; she asks if they brought anyone else. Megan and Cueball say they're trying to find out why the sea is changing. The woman explains that there is another sea which was once connected to theirs, but has since been cut off. She says that the water is now flowing back into their sea, and that the level will continue to rise. She shows Megan and Cueball a map of the area, including the castle, their sea, and the bigger sea which is joining it. The woman then shows the predicted new shoreline, which closely resembles that of the Mediterranean Sea. Megan assumes that the level rise is slow and will last for some years. The woman disagrees, and explains that the water level will rise over the course of a few days. Faced with knowledge of the imminent destruction of their village, Megan and Cueball bolt from the room and begin to run.
They leave the castle and run back the same way as they came. They encounter some people on their way out. By this time the title text has changed from 'Wait for it' to '...' to 'RUN.' They pass some more people they met before and when they are alone, Megan reveals that she has stolen the maps from the long-haired woman. Megan hopes she can give them back sometime. Cueball is happy and they continue their journey by using the maps. They reach their village, where they find that the people are aware of the rising sea levels, and that some of them have already gone up into the now-abandoned hills to see what items were left behind. Megan and Cueball tell them that the sea will continue to rise, and they make preparations to evacuate uphill.
It turns out that LaPetite has turned Megan and Cueball's sandcastle into a boat. Megan has the idea to ride it on the rising waters, but they need to hurry to prepare it.
The raft is hastily made seaworthy and the tribe goes off in pursuit of the rest. They find the others floating on a makeshift canoe from a piece of floating debris. A rope is thrown and the two boats try to pull each other closer. At one point the boats bump into each other and everyone falls over. A new day arises and as Cueball and Megan rebuild their sandcastle on top of the raft, the raft runs aground. The tribe rushes off to explore the new land, and the raft is left behind at the end of the story at the mercy of the wind and waves.